U.S. Pat. Nos. 3,661,570 to Moss and 3,676,610 to Moss et al, incorporated herein by reference, describe methods of making alloys of iron, silicon and aluminum containing a dispersed second phase of an oxide for use in magnetic record-playback heads having improved wear properties. According to the process described in U.S. Pat. No. 3,661,570, small particles of a magnetic iron-silicon-aluminum alloy were milled in alcohol solution containing about 20 volume percent of water to reduce the particle size to less than 44 microns, preferably less than 20 microns, while oxidizing the particles so that they have a thin layer about 2 microns thick of oxide on the outside of the particles. The particles were then densified, as by hot pressing at about 1000.degree. C. and about 15,000 psi pressure, for an hour. The presence of the oxide serves to increase the hardness of the alloy to from about 48 to about 50 hardness on the Rockwell "C" scale, with resultant decrease in wear of record-playback heads made therefrom.
In an alternate method of preparing these oxidized alloys, U.S. Pat. Nos. 3,739,445 and 3,814,598 to Gabriel et al. describe a thermal process whereby finely divided iron-silicon-aluminum alloy powders having a particle size of about 10-20 microns prepared by atomizing the molten alloy, separating and milling oversize particles in dry alcohol and combining them with unmilled particles, are oxidized by heating at about 600.degree. F. for an hour in air. The oxidized particles contain from about 3400-4400 parts per million of oxygen. These oxide powders are then hot pressed in a manner similar to that taught in the above-described Moss patents to form alloys also having a Rockwell "C" hardness of about 50.